Transforming growth factor-{beta} coordinately induces suppressor of cytokine signaling 3 and leukemia inhibitory factor to suppress osteoclast apoptosis

Endocrinology. 2010 Apr;151(4):1713-22. doi: 10.1210/en.2009-0813. Epub 2010 Feb 24.

Abstract

Local release of TGF-beta during times of high bone turnover leads to elevated levels within the bone microenvironment, and we have shown that TGF-beta suppresses osteoclast apoptosis. Therefore, understanding the influences of TGF-beta on bone resorbing osteoclasts is critical to the design of therapies to reduce excess bone loss. Here we investigated the mechanisms by which TGF-beta sustains suppression of osteoclast apoptosis. We found TGF-beta rapidly increased leukemia inhibitory factor (LIF) expression and secretion by phosphorylated mothers against decapentaplegic-dependent and -independent signaling pathways. TGF-beta also induced suppressor of cytokine signaling 3 (SOCS3) expression, which was required for TGF-beta or LIF to promote osteoclast survival by. Blocking LIF or SOCS3 blocked TGF-beta promotion of osteoclast survival, confirming that LIF and SOCS3 expression are necessary for TGF-beta-mediated suppression of osteoclast apoptosis. Investigation of the mechanisms by which LIF promotes osteoclast survival revealed that LIF-induced expression of Bcl-X(L) and repressed Bcl-2 interacting domain expression by activating MAPK kinase, AKT, and nuclear factor-kappaB pathways. Suppression of Janus kinase/signal transducer and activator of transcription signaling further increased Bcl-X(L) expression and enhanced osteoclast survival, supporting that this pathway is not involved in prosurvival effects of TGF-beta and LIF. These data show that TGF-beta coordinately induces LIF and SOCS3 to promote prosurvival signaling. This alters the ratio of prosurvival Bcl2 family member Bcl-X(L) to proapoptotic family member Bcl-2 interacting domain, leading to prolonged osteoclast survival.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Analysis of Variance
  • Animals
  • Apoptosis / drug effects
  • Blotting, Western
  • Cell Survival / drug effects
  • Cells, Cultured
  • Enzyme-Linked Immunosorbent Assay
  • Leukemia Inhibitory Factor / metabolism*
  • Mice
  • NF-kappa B / metabolism
  • Osteoclasts / drug effects
  • Osteoclasts / metabolism
  • Osteoclasts / pathology*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA, Small Interfering / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Smad Proteins / metabolism
  • Suppressor of Cytokine Signaling Proteins / metabolism*
  • Time Factors
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta / pharmacology
  • bcl-X Protein / metabolism

Substances

  • Leukemia Inhibitory Factor
  • NF-kappa B
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Small Interfering
  • Smad Proteins
  • Suppressor of Cytokine Signaling Proteins
  • Transforming Growth Factor beta
  • bcl-X Protein
  • Proto-Oncogene Proteins c-akt